Auto merge of #129183 - estebank:cfg-visitor, r=davidtwco

Detect more `cfg`d out items in resolution errors

Use a visitor to collect *all* items (including those nested) that were stripped behind a `cfg` condition.

```
error[E0425]: cannot find function `f` in this scope
  --> $DIR/nested-cfg-attrs.rs:4:13
   |
LL | fn main() { f() }
   |             ^ not found in this scope
   |
note: found an item that was configured out
  --> $DIR/nested-cfg-attrs.rs:2:4
   |
LL | fn f() {}
   |    ^
note: the item is gated here
  --> $DIR/nested-cfg-attrs.rs:1:35
   |
LL | #[cfg_attr(all(), cfg_attr(all(), cfg(FALSE)))]
   |                                   ^^^^^^^^^^
```

Author: bors

compiler/rustc_expand/src/expand.rs

@@ -1411,9 +1411,8 @@ impl InvocationCollectorNode for P<ast::Item> {
                     }
                 }
             }
-
             let mut idents = Vec::new();
-            collect_use_tree_leaves(ut, &mut idents);
+            collect_use_tree_leaves(&ut, &mut idents);
             idents
         } else {
             self.kind.ident().into_iter().collect()

compiler/rustc_resolve/src/diagnostics.rs

@@ -801,10 +801,12 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                     err.multipart_suggestion(msg, suggestions, applicability);
                 }
-                if let Some(ModuleOrUniformRoot::Module(module)) = module
-                    && let Some(module) = module.opt_def_id()
-                    && let Some(segment) = segment
-                {
+
+                if let Some(segment) = segment {
+                    let module = match module {
+                        Some(ModuleOrUniformRoot::Module(m)) if let Some(id) = m.opt_def_id() => id,
+                        _ => CRATE_DEF_ID.to_def_id(),
+                    };
                     self.find_cfg_stripped(&mut err, &segment, module);
                 }
 
@@ -2839,16 +2841,13 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 continue;
             }
 
-            let note = errors::FoundItemConfigureOut { span: ident.span };
-            err.subdiagnostic(note);
-
-            if let CfgEntry::NameValue { value: Some((feature, _)), .. } = cfg.0 {
-                let note = errors::ItemWasBehindFeature { feature, span: cfg.1 };
-                err.subdiagnostic(note);
+            let item_was = if let CfgEntry::NameValue { value: Some((feature, _)), .. } = cfg.0 {
+                errors::ItemWas::BehindFeature { feature, span: cfg.1 }
             } else {
-                let note = errors::ItemWasCfgOut { span: cfg.1 };
-                err.subdiagnostic(note);
-            }
+                errors::ItemWas::CfgOut { span: cfg.1 }
+            };
+            let note = errors::FoundItemConfigureOut { span: ident.span, item_was };
+            err.subdiagnostic(note);
         }
     }
 }

compiler/rustc_resolve/src/errors.rs

@@ -1,10 +1,13 @@
 use rustc_errors::codes::*;
-use rustc_errors::{Applicability, ElidedLifetimeInPathSubdiag, MultiSpan};
+use rustc_errors::{
+    Applicability, Diag, ElidedLifetimeInPathSubdiag, EmissionGuarantee, IntoDiagArg, MultiSpan,
+    Subdiagnostic,
+};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Ident, Span, Symbol};
 
-use crate::Res;
 use crate::late::PatternSource;
+use crate::{Res, fluent_generated as fluent};
 
 #[derive(Diagnostic)]
 #[diag(resolve_generic_params_from_outer_item, code = E0401)]
@@ -1201,26 +1204,35 @@ pub(crate) struct IdentInScopeButItIsDesc<'a> {
     pub(crate) imported_ident_desc: &'a str,
 }
 
-#[derive(Subdiagnostic)]
-#[note(resolve_found_an_item_configured_out)]
 pub(crate) struct FoundItemConfigureOut {
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Subdiagnostic)]
-#[note(resolve_item_was_behind_feature)]
-pub(crate) struct ItemWasBehindFeature {
-    pub(crate) feature: Symbol,
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Subdiagnostic)]
-#[note(resolve_item_was_cfg_out)]
-pub(crate) struct ItemWasCfgOut {
-    #[primary_span]
     pub(crate) span: Span,
+    pub(crate) item_was: ItemWas,
+}
+
+pub(crate) enum ItemWas {
+    BehindFeature { feature: Symbol, span: Span },
+    CfgOut { span: Span },
+}
+
+impl Subdiagnostic for FoundItemConfigureOut {
+    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
+        let mut multispan: MultiSpan = self.span.into();
+        match self.item_was {
+            ItemWas::BehindFeature { feature, span } => {
+                let key = "feature".into();
+                let value = feature.into_diag_arg(&mut None);
+                let msg = diag.dcx.eagerly_translate_to_string(
+                    fluent::resolve_item_was_behind_feature,
+                    [(&key, &value)].into_iter(),
+                );
+                multispan.push_span_label(span, msg);
+            }
+            ItemWas::CfgOut { span } => {
+                multispan.push_span_label(span, fluent::resolve_item_was_cfg_out);
+            }
+        }
+        diag.span_note(multispan, fluent::resolve_found_an_item_configured_out);
+    }
 }
 
 #[derive(Diagnostic)]

compiler/rustc_resolve/src/late.rs

@@ -4231,13 +4231,21 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 //
                 // And that's what happens below - we're just mixing both messages
                 // into a single one.
+                let failed_to_resolve = match parent_err.node {
+                    ResolutionError::FailedToResolve { .. } => true,
+                    _ => false,
+                };
                 let mut parent_err = this.r.into_struct_error(parent_err.span, parent_err.node);
 
                 // overwrite all properties with the parent's error message
                 err.messages = take(&mut parent_err.messages);
                 err.code = take(&mut parent_err.code);
                 swap(&mut err.span, &mut parent_err.span);
-                err.children = take(&mut parent_err.children);
+                if failed_to_resolve {
+                    err.children = take(&mut parent_err.children);
+                } else {
+                    err.children.append(&mut parent_err.children);
+                }
                 err.sort_span = parent_err.sort_span;
                 err.is_lint = parent_err.is_lint.clone();
 

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -525,9 +525,8 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         }
         self.err_code_special_cases(&mut err, source, path, span);
 
-        if let Some(module) = base_error.module {
-            self.r.find_cfg_stripped(&mut err, &path.last().unwrap().ident.name, module);
-        }
+        let module = base_error.module.unwrap_or_else(|| CRATE_DEF_ID.to_def_id());
+        self.r.find_cfg_stripped(&mut err, &path.last().unwrap().ident.name, module);
 
         (err, candidates)
     }

tests/ui/cfg/both-true-false.stderr

@@ -3,6 +3,22 @@ error[E0425]: cannot find function `foo` in this scope
    |
 LL |     foo();
    |     ^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/both-true-false.rs:6:4
+   |
+LL | #[cfg(false)]
+   |       ----- the item is gated here
+LL | #[cfg(true)]
+LL | fn foo() {}
+   |    ^^^
+note: found an item that was configured out
+  --> $DIR/both-true-false.rs:10:4
+   |
+LL | #[cfg(false)]
+   |       ----- the item is gated here
+LL | fn foo() {}
+   |    ^^^
 
 error: aborting due to 1 previous error
 

tests/ui/cfg/cfg-version/syntax.stderr

@@ -128,60 +128,150 @@ error[E0425]: cannot find function `key_value_form` in this scope
    |
 LL |     key_value_form();
    |     ^^^^^^^^^^^^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/syntax.rs:32:4
+   |
+LL | #[cfg(version = "1.43")]
+   |       ---------------- the item is gated behind the `1.43` feature
+LL |
+LL | fn key_value_form() {}
+   |    ^^^^^^^^^^^^^^
 
 error[E0425]: cannot find function `not_numbers_or_periods` in this scope
   --> $DIR/syntax.rs:143:5
    |
 LL |     not_numbers_or_periods();
    |     ^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/syntax.rs:53:4
+   |
+LL | #[cfg(version("foo"))]
+   |              ------- the item is gated here
+LL |
+LL | fn not_numbers_or_periods() {}
+   |    ^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0425]: cannot find function `complex_semver_with_metadata` in this scope
   --> $DIR/syntax.rs:144:5
    |
 LL |     complex_semver_with_metadata();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/syntax.rs:57:4
+   |
+LL | #[cfg(version("1.20.0-stable"))]
+   |              ----------------- the item is gated here
+LL |
+LL | fn complex_semver_with_metadata() {}
+   |    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0425]: cannot find function `invalid_major_only` in this scope
   --> $DIR/syntax.rs:145:5
    |
 LL |     invalid_major_only();
    |     ^^^^^^^^^^^^^^^^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/syntax.rs:80:4
+   |
+LL | #[cfg(version("1"))]
+   |              ----- the item is gated here
+LL |
+LL | fn invalid_major_only() {}
+   |    ^^^^^^^^^^^^^^^^^^
 
 error[E0425]: cannot find function `invalid_major_only_zero` in this scope
   --> $DIR/syntax.rs:146:5
    |
 LL |     invalid_major_only_zero();
    |     ^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/syntax.rs:84:4
+   |
+LL | #[cfg(version("0"))]
+   |              ----- the item is gated here
+LL |
+LL | fn invalid_major_only_zero() {}
+   |    ^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0425]: cannot find function `invalid_major_only_negative` in this scope
   --> $DIR/syntax.rs:147:5
    |
 LL |     invalid_major_only_negative();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/syntax.rs:97:4
+   |
+LL | #[cfg(version("-1"))]
+   |              ------ the item is gated here
+LL |
+LL | fn invalid_major_only_negative() {}
+   |    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0425]: cannot find function `exceed_u16_major` in this scope
   --> $DIR/syntax.rs:148:5
    |
 LL |     exceed_u16_major();
    |     ^^^^^^^^^^^^^^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/syntax.rs:103:4
+   |
+LL | #[cfg(version("65536"))]
+   |              --------- the item is gated here
+LL |
+LL | fn exceed_u16_major() {}
+   |    ^^^^^^^^^^^^^^^^
 
 error[E0425]: cannot find function `exceed_u16_minor` in this scope
   --> $DIR/syntax.rs:149:5
    |
 LL |     exceed_u16_minor();
    |     ^^^^^^^^^^^^^^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/syntax.rs:107:4
+   |
+LL | #[cfg(version("1.65536.0"))]
+   |              ------------- the item is gated here
+LL |
+LL | fn exceed_u16_minor() {}
+   |    ^^^^^^^^^^^^^^^^
 
 error[E0425]: cannot find function `exceed_u16_patch` in this scope
   --> $DIR/syntax.rs:150:5
    |
 LL |     exceed_u16_patch();
    |     ^^^^^^^^^^^^^^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/syntax.rs:111:4
+   |
+LL | #[cfg(version("1.0.65536"))]
+   |              ------------- the item is gated here
+LL |
+LL | fn exceed_u16_patch() {}
+   |    ^^^^^^^^^^^^^^^^
 
 error[E0425]: cannot find function `exceed_u16_mixed` in this scope
   --> $DIR/syntax.rs:151:5
    |
 LL |     exceed_u16_mixed();
    |     ^^^^^^^^^^^^^^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/syntax.rs:115:4
+   |
+LL | #[cfg(version("65536.0.65536"))]
+   |              ----------------- the item is gated here
+LL |
+LL | fn exceed_u16_mixed() {}
+   |    ^^^^^^^^^^^^^^^^
 
 error: aborting due to 14 previous errors; 14 warnings emitted
 

tests/ui/cfg/cmdline-false.stderr

@@ -3,6 +3,14 @@ error[E0425]: cannot find function `foo` in this scope
    |
 LL |     foo();
    |     ^^^ not found in this scope
+   |
+note: found an item that was configured out
+  --> $DIR/cmdline-false.rs:5:4
+   |
+LL | #[cfg(false)]
+   |       ----- the item is gated here
+LL | fn foo() {}
+   |    ^^^
 
 error: aborting due to 1 previous error
 

tests/ui/cfg/diagnostics-cross-crate.rs

@@ -11,24 +11,20 @@ fn main() {
     cfged_out::inner::uwu(); //~ ERROR cannot find function
     //~^ NOTE found an item that was configured out
     //~| NOTE not found in `cfged_out::inner`
-    //~| NOTE the item is gated here
 
     // The module isn't found - we would like to get a diagnostic, but currently don't due to
     // the awkward way the resolver diagnostics are currently implemented.
     cfged_out::inner::doesnt_exist::hello(); //~ ERROR failed to resolve
     //~^ NOTE could not find `doesnt_exist` in `inner`
     //~| NOTE found an item that was configured out
-    //~| NOTE the item is gated here
 
     // It should find the one in the right module, not the wrong one.
     cfged_out::inner::right::meow(); //~ ERROR cannot find function
     //~^ NOTE found an item that was configured out
     //~| NOTE not found in `cfged_out::inner::right
-    //~| NOTE the item is gated behind the `what-a-cool-feature` feature
 
     // Exists in the crate root - diagnostic.
     cfged_out::vanished(); //~ ERROR cannot find function
     //~^ NOTE found an item that was configured out
     //~| NOTE not found in `cfged_out`
-    //~| NOTE the item is gated here
 }